Article

Direct and indirect roles of viral suppressors of RNA silencing in pathogenesis.

Center for Plant Cell Biology, Department of Plant Pathology and Microbiology, University of California, Riverside, California 92521, USA.
Annual Review of Phytopathology (Impact Factor: 11). 10/2008; 46:303-26. DOI: 10.1146/annurev.phyto.46.081407.104746
Source: PubMed

ABSTRACT Plant and animal viruses overcome host antiviral silencing by encoding diverse viral suppressors of RNA silencing (VSRs). Prior to the identification and characterization of their silencing suppression activities mostly in transgene silencing assays, plant VSRs were known to enhance virus accumulation in the inoculated protoplasts, promote cell-to-cell virus movement in the inoculated leaves, facilitate the phloem-dependent long-distance virus spread, and/or intensify disease symptoms in systemically infected tissues. Here we discuss how the various silencing suppression activities of VSRs may facilitate these distinct steps during plant infection and why VSRs may not play a direct role in eliciting disease symptoms by general impairments of host endogenous small RNA pathways. We also highlight many of the key questions still to be addressed on the role of viral suppression of antiviral silencing in plant infection.

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    • "From almost all virus genus that infect plants, over 50 individual VSRs have been identified, strongly suggesting that successful virus infection requires their expression [47] [55]. The data available in the literature suggest that almost all viruses encode at least one suppressor, but in many cases, viruses encode more than one [47]. "
    Current Issues in Molecular Virology - Viral Genetics and Biotechnological Applications, Edited by Victor Romanowski, 11/2013: chapter 11: pages 251-285; , ISBN: ISBN 978-953-51-1207-5
    • "Cleavage of viral RNA results in reduction of virus titers in local and distant leaves and plant recovery phenotype (Godge et al. 2008). At the same time, all RNA virus-derived expression vectors will not be useful as silencing vectors because many have potent anti-silencing proteins, which directly interfere with host silencing machinery (Diaz-pendon and Ding 2008). Similarly, DNA viruses have not been used extensively as expression vectors due to their size constraints for movement (Wani and Sanghera, 2010). "
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    • "Cleavage of viral RNA results in reduction of virus titers in local and distant leaves and plant recovery phenotype (Godge et al. 2008). At the same time, all RNA virus-derived expression vectors will not be useful as silencing vectors because many have potent anti-silencing proteins, which directly interfere with host silencing machinery (Diaz-pendon and Ding 2008). Similarly, DNA viruses have not been used extensively as expression vectors due to their size constraints for movement (Wani and Sanghera, 2010). "
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    ABSTRACT: Plant diseases are significant threats to modern agriculture and their control remains a challenge to the management of cultivation. Therefore, plant disease management has always been one of the main objectives of any crop improvement programme. To reduce the losses caused by plant diseases, plant biologists have adopted numerous methods to engineer resistant plants. Among them, RNA silencing-based resistance has been a powerful tool that has been used to engineer resistant crops during the last two decades. Engineered plants in particular plants expressing RNA-silencing nucleotides are becoming increasingly important and are likely to provide more effective strategies in future. The advantage of RNAi as a novel gene therapy against fungal, viral and bacterial infection in plants lies in the fact that it regulates gene expression via mRNA degradation, translation repression and chromatin remodelling through small non-coding RNAs. Mechanistically, the silencing processes are guided by processing products of the dsRNA trigger, which are known as small interfering RNAs and microRNAs. The application of tissue-specific or inducible gene silencing, with the use of appropriate promoters to silence several genes simultaneously should enhance researchers’ ability to protect crops against diseases. This reviews a general discussion on the development of RNAi and role of RNAi in plant disease management
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